There is no doubt that solar ultraviolet (UV) exposure is the most important environmental risk factor for the development of non-
melanoma skin cancer. Therefore, sun protection is of particular importance to prevent these
malignancies, especially in risk groups. However, 90% of all requisite
vitamin D has to be formed in the skin through the action of the sun-a serious problem, for a connection between
vitamin D deficiency and a broad variety of independent diseases including various types of
cancer,
bone diseases,
autoimmune diseases,
hypertension and
cardiovascular disease has now been clearly indicated in a large number of epidemiologic and laboratory studies. An important link that improved our understanding of these new findings was the discovery that the biologically active
vitamin D metabolite
1,25(OH)(2)D is not exclusively produced in the kidney, but in many other tissues such as prostate, colon, skin and osteoblasts. Extra-renally produced
1,25(OH)(2)D is now considered to be an autocrine or paracrine
hormone, regulating various cellular functions including cell growth. We and others have shown that strict sun protection causes
vitamin D deficiency in risk groups. In the light of new scientific findings that convincingly demonstrate an association of
vitamin D deficiency with a variety of severe diseases including various
cancers, the detection and treatment of
vitamin D deficiency in sun-deprived risk groups is of high importance. It has to be emphasized that in groups that are at high risk of developing
vitamin D deficiency (e.g.,
nursing home residents or patients under immunosuppressive therapy),
vitamin D status has to be monitored.
Vitamin D deficiency should be treated, e.g., by giving
vitamin D orally. Dermatologists and other clinicians have to recognize that there is convincing evidence that the protective effect of less intense solar UV radiation outweighs its mutagenic effects. Although further work is necessary to define an adequate
vitamin D status and adequate guidelines for solar UV exposure, it is at present mandatory that public health campaigns and recommendations of dermatologists on sun protection consider these facts. Well-balanced recommendations on sun protection have to ensure an adequate
vitamin D status, thereby protecting people against adverse effects of strict sun protection without significantly increasing the risk of developing UV-induced
skin cancer.